The present invention relates to an electronic thermometer, and in particular to an electronic thermometer which has different display resolutions depending upon temperature.
A conventional electronic thermometer typically senses temperature at its temperature sensing unit, which may comprise a temperature sensitive unit such as a thermistor, and outputs a digital signal corresponding to the sensed temperature. Then another unit of the thermometer reads out temperature conversion data which is previously stored in a memory means such as a ROM in advance, according to the value of a digital signal corresponding to said digital signal output by said temperature sensing unit. The read out temperature conversion data is then displayed on a display unit.
A typical such conventional electronic thermometer, which is a clinical thermometer, has a preset measuring range of for example from 35.degree. to 42.degree. Celsius, and does not display any specific temperature when the sensed temperature by the temperature sensitive unit is outside this range. Thus, for example, during the initial stage of measurement when the temperature sensed by the temperature sensitive means is low, only an indication of "L" is displayed on the display unit, and, once said temperature sensed by the temperature sensitive means becomes higher than 35.degree. C., a specific temperature reading at a specific digitized resolution is displayed from then on.
According to such a conventional type of electronic clinical thermometer, the measurement resolution is thus decided to be, for example, 0.01.degree. C., and then temperature readings are displayed for every 0.01.degree. C. when the sensed temperature is in the temperature range for which indication is to be given. For example, temperature conversion data is required to be stored at steps of 0.01.degree. C. for the entire range of 35.degree. C. to 42.degree. C. This requires a great deal of memory space, which is not actually being effectively utilized, since in the exemplary case of a clinical thermometer such a very accurate reading in the case that the sensed temperature is very wide of the typical body temperature of a human being is not actually required. If the range of measurement indication is to be expanded yet further, then this gives rise to the problem of requiring an expanded memory capacity for storing an accordingly large conversion data volume.
Further, in the case of a clinical thermometer which has a high resolution around the range of temperatures which a human body may have, if in view of memory limitations this measurement range is restricted, then the response time from the start of measurement to the appearance of a definite temperature on the display unit tends to become long, in other words the indication of "L" on the display unit persists for a long time, and the user tends to become irritated by this fact.